1. Field of the Invention
The present invention relates to an airbag designed to protect the occupants of a vehicle during a collision. More specifically, the invention relates to a rigid knee airbag that is dent and vibration resistant.
2. Technical Background
Inflatable airbags enjoy widespread acceptance as passive passenger restraints for use in motor vehicles. This acceptance has come as airbags have built a reputation of preventing numerous deaths and injuries over years of development, testing, and use. Studies show that in some instances, the use of frontally placed vehicular airbags can reduce the number of fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Other statistics suggest that in a frontal collision, the combination of a seat belt and an airbag can reduce the incidence of serious chest injuries by 65% and the incidence of serious head injuries by up to 75%. These numbers, and the thousands of prevented injuries they represent, demonstrate the life-saving potential of airbags and the need to encourage their use, production, and development.
Airbags are often installed in the steering wheel and in the dashboard on the passenger side of a car. These airbags are used for the primary deceleration of a vehicle occupant since, in a large percentage of collisions, the occupant is accelerated forward within the vehicle. Such airbags are generally housed within the dashboard, steering wheel, or other similar interior panels of a vehicle, and are covered by a trim cover panel. The trim cover panel covers the compartment that contains the airbag module. Such airbag covers are typically made of rigid plastic, and are configured to be opened by the pressure created by the deploying airbag. During deployment of the airbag, it is preferable to retain the airbag cover in at least partial attachment to the vehicle to prevent the airbag cover from flying loose in the passenger compartment.
Airbags are generally linked to a control system within the vehicle that triggers their initiation when a collision occurs. Generally, an accelerometer within the vehicle measures the abnormal deceleration caused by the collision event and triggers the ignition of an airbag inflator. This control system is often referred to as an electronic control unit (xe2x80x9cECUxe2x80x9d). The ECU includes a sensor that continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor that uses an algorithm to determine whether a collision has occurred.
When the processor of the ECU determines that the vehicle is experiencing a collision, the ECU transmits an electrical signal to an initiator assembly, which is connected to an inflator that is coupled to the airbag module. The initiator activates the inflator. An inflator is a gas generator that typically uses a compressed or liquefied gas or a mixture of gases, a solid fuel, or some combination of the two, to rapidly generate a large volume of inflation gas. The gas is then channeled, often through a segment of specialized tubing called a gas guide, into the airbag. The gas inflates the airbag, thus placing it in the path of the vehicle occupant and allowing it to absorb the impact of the vehicle occupant.
As experience with the manufacture and use of airbags has progressed, the engineering challenges involved in their design, construction, and use have become better understood. First, most airbag systems are designed to rapidly inflate and provide a cushion in front of or alongside an occupant based on a presumption that the occupant will be in a predetermined position. Problems have been noted to occur when the occupant is xe2x80x9cout of positionxe2x80x9d with regard to this presumed placement when a collision. event occurs and the airbag deploys. Similarly, problems may occur when the occupant, though possibly at first in the predicted position, strikes a glancing blow to the airbag, and is then deflected away from the airbag before proper deceleration can occur.
Out-of-position injuries may be attributed in part to the fact that most airbag systems have been primarily designed for deployment in front of the torso of an occupant. More specifically, such airbags are disposed for deployment between the upper torso of an occupant and the windshield and instrument panel. During a front-end collision, there is a tendency for an occupant, particularly one who is not properly restrained by a seat belt, to slide forward along the seat. This results in poor kinematics and positioning when the occupant interacts with a frontal airbag, such as a driver""s side or passenger""s side airbag.
In order to avoid such dangers to occupants, knee airbag systems have been developed. These airbags deploy during a collision event and engage an occupant""s knees or lower legs. This holds the occupant in place on the seat, and improves the kinematics of the occupant.
Such knee airbag systems include a knee airbag and a panel, referred to as a knee bolster panel, which is disposed in front of the knee airbag. The addition of a knee bolster panel to the airbag provides a more rigid surface area to better engage and decelerate the knees or legs of an occupant and thereby restrain the occupant""s lower body. Additionally, the knee bolster panel allows some degree of deformation to minimize the impact of an occupant.
Such knee airbag systems, like many other airbag systems, suffer from high costs and engineering problems. Specifically, knee airbags are difficult to mount in the tight spaces available under the steering column or dashboard. Further, many current knee airbag systems use an inflator located at a remote location. Such systems require the use of costly gas guides suitable for conducting hot inflation gases from the inflator to the airbag. Additionally, the airbags themselves must be treated with various coatings to protect the fabric of the airbag itself from the heat of the gas. Also, in some specific applications, such as mounting an airbag in the door of a glove box of a vehicle, fabric airbags have proven very difficult to install.
To both automobile manufacturers and consumers, aesthetic aspects of a knee airbag system are also important. For example, the visible portion of a stored knee airbag module in a vehicle must be both durable and attractive prior to deployment of the airbag. Otherwise, automobile manufacturers will be slow to incorporate these types of airbags into their vehicles and may seek out alternative technologies that do not adversely impact the appearance of the vehicle. Furthermore, if a stored airbag module vibrates during operation of the vehicle in which it is located, the vibration may produce undesired noise. Automobile owners may believe that the generated noise indicates that something is mechanically wrong with the vehicle. Of course, automobile manufacturers would quickly discontinue using an airbag module that generates unwanted vibrations and noise.
Thus, it would be an advancement in the art to provide an inflatable rigid knee airbag system to protect a vehicle occupant in collision events in a wide variety of situations. Specifically, it would be an advancement in the art to provide a knee airbag suitable for mounting in a vehicle under the steering column or dashboard, including mounting in a glove box door. It would also be an advancement in the art to provide a knee airbag system that permits direct mounting of the inflator to the airbag. Additionally, it would be an advancement in the art to provide a knee airbag system having a visible portion which is both durable and aesthetically pleasing. It would also be an advancement in the art if the knee airbag system is resistant to vibration and thus does not produce unwanted noise.
The apparatus and method of the present invention have been developed in response to the present state of the art, and in particular, in response to problems and needs in the art that have not yet been fully solved by currently available airbag systems. More specifically, the inflatable rigid knee airbag system provides a versatile and low-cost airbag module that does not generate unwanted vibration or noise.
The inflatable rigid knee airbag system includes a rear panel and a front panel. The rear and front panels are generally planar and are formed from a substantially rigid material, such as sheet metal. The front panel may have various shapes such as rectangular, square or elliptical. The rear and front panels are attached to each other generally around their respective perimeters to define an inflatable chamber. Various methods of attachment may be used within the scope of this invention. For instance, a series of spot welds may be used to secure the front and rear panels to each other.
The rear panel is folded such that it expands, or unfolds, when inflatable gas is injected into the inflatable chamber. More specifically, the rear panel includes both vertical folds and accordion folds. Prior to inflation of the inflatable chamber, the vertical folds include three fold lines that form a generally A-frame shaped ridge. The accordion folds include two fold lines that define an accordion type fold. The vertical folds and accordion folds expand, at least partially unfold, when gas is forced into the inflatable chamber.
The rear panel also includes a rectangular orifice for interfacing with an adapter unit. The adapter unit includes a hollow rigid box that is seated within the rectangular orifice of the rear panel. A series of connector studs on the adapter unit are positioned within mating orifices on the rear panel. Nuts, or other securing devices, attached to the connector studs secure the adapter unit to the rear panel. Other securing mechanisms or techniques, such spot welds, may be used to secure the adaptor unit to the rear panel. An inflator is positioned within the orifice of the hollow rigid box such that the inflator is in fluid communication with the inflatable chamber.
A support core is positioned between the rear and front panels. The support core substantially occupies the inflatable chamber defined by the front and rear panels. The support core may be made from an injected or a pre-formed foam that is heat resistant, such as a phenolic foam. The shape of the pre-formed foam is defined before placement into the inflatable chamber. The injected foam, on the other hand, is poured or blown in a liquid or semi-liquid state into the inflatable chamber. The support core is attached to either the front or rear panel, both the front and rear panels, or neither of the panels.
The support core may be designed to break into smaller pieces in response to injection of inflatable gas into the inflatable chamber. The support core may also include a recess into which inflatable gas will initially be directed to facilitate breaking the support core into smaller pieces. Alternatively, the support core may be designed to remain in substantially a single piece during inflation of the inflatable chamber. This may be achieved by attaching the support to the front panel, but not the rear panel, and by forming the support core from a substantially resilient material.
The support core serves at least two purposes. First, the support core provides support to the front panel to limit denting of the front panel prior to deployment of the inflatable rigid knee airbag system. This support enhances the aesthetic appearance of the front panel, the portion of the airbag system that is visible to an occupant of the vehicle. Second, the support core separates the front and rear panels from each other to prevent the panels from vibrating against each other and generating unwanted noise. Additionally, attachment of the support core to either the front panel or rear panel further limits undesirable vibration and noise.
The front panel may be attached to, or integrated with, a decorative trim panel. The decorative trim panel can be a glove box door cover or other interior panel for the vehicle. The decorative trim panel may be attached to the front panel using various fastening techniques, such as rivets, snap-fitting devices, spot welding, and thermoplastic welding techniques. The decorative trim panel also functions as a knee bolster that deforms slightly in response to an impact of a vehicle occupant to dissipate the energy of the impact and minimize potential injuries to the occupant. The decorative trim panel can be produced by a number of known techniques, such as thermoplastic injection-molding or a skin and foam molding process commonly employed in the automotive industry.
An alternative embodiment of the inflatable rigid knee airbag system includes a front panel, a rear panel, and an extensible bellows panel. The front, rear, and bellows panels may each be formed from a substantially rigid material, again such as sheet metal.
The front, rear, and bellows panels define an inflatable chamber. The front and rear panels are substantially planar in shape. The bellows panel is positioned between the front and rear panels and is attached to the perimeter of the front and rear panels to define the inflatable chamber. The bellows panel may be positioned in a compact or an inflated position. When inflatable gas is forcefully injected into the inflatable chamber the bellows panel at least partially unfolds, expanding the inflatable chamber.
An inflator is secured within an opening in the rear panel such that the inflator is at least partially positioned within the inflatable chamber. More specifically, gas exit ports on the inflator are positioned within the inflatable chamber to enable rapid inflation of the chamber.
As in the first embodiment of the inflatable rigid knee airbag system, a support core is positioned between the front and rear panels to dampen vibration and to provide support to the front panel to minimize unsightly denting. Again, the support core may be made from various types of foam, e.g., injected or pre-formed foam. The support core may include a recess to facilitate breaking the support core into smaller pieces during inflation of the inflatable chamber. Alternatively, the support core may be designed to remain in substantially a single piece during inflation of the inflatable chamber.
In view of the foregoing, the inflatable rigid knee airbag system provides substantial advantages over conventional airbag systems. The inflatable rigid knee airbag system is versatile and may be positioned within various locations in a vehicle, such as in a glove box door or underneath the steering wheel. The inflatable chamber of the inflatable rigid knee airbag system may be formed from a rigid material, such as sheet metal, thus avoiding the need for expensive heat-resistant fabrics or treatments. The support core minimizes the danger of denting to the front panel and dampens vibration to limit unwanted noise when the inflatable rigid knee airbag system is in a pre-deployment state.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.